Cutting oil



number between about 100 and 250.

Patented Nov. 6, 1945 UNITED STATES PATENT OFFICE CUTTING OIL Leslie R.Raymond, Santa Ana, Calif., assignor to A. S. Cowie & 00., Los Angeles,Calif., a corporation of California No Drawing. Application August 21,1944, Serial No. 550,485

6 Claims.

smoother and more perfect surfaces on the. work:-

Many different types of compositions have been used for cutting oils.Mineral oils have been used for light duty cutting, Where therequirements for lubrication and cooling are not severe, but have notbeen found satisfactory for more difficult machining operations. Wheretherequirements for cooling and lubrication are severe, the compositionsused have generally consisted principally of animal or vegetable oils,and sulphur is often added for the purpose of increasing the filmstrength. Vegetable or animal oils have certain disadvantages, however,including objectionable odor and a tendency to become rancid.

The principal object of this invention is to provide a cutting oil whicheffectively performs the above mentioned functions and which does notrequire the use of animal or vegetable oil or the addition of sulphur.

A particular object is to provide a cuttin oil composition whichprovides a highly effective lubricatingand protective film on both thework and the tool.

The cutting oil of my present invention consists principally of minerallubricating oil and naphthenic acid and contains, in addition, areltively small proportion of metallic naphthenate dissolved orcolloidally dispersed therein.

The term mineral lubricating oil is used herein to designate a petroleumoil, either paraffin base or naphthene base, which has some lubricatingvalue, including products commonly used as lubricating oils as well asoils of lower boiling point and lower viscosity, such as gas oil,kerosene or kerosene distillate.

Naphthenic acids are derived from naphthene base petroleum oils andusually comprise a number of different compounds rather than a singlecompound. The naphthenic acids which I have found suitable for purposesof my invention have an acid number from about 75 to about 375, althoughthe best results are usually obtained by the use of a naphthenic acidhaving an acid For example, I have obtained excellent results with anaphthenic acid having an acid number of approximately 100, which wouldcorrespond approximately to an acid having the formula CssHnCOOH This ofcourse is not the true formula but represents approximately the averageformula of the acids present in the material.

The proportions of mineral lubricating oil and naphthenic acid aresubject to considerable variation. These materials are freely misciblewith or soluble in one another in any proportions.

the cutting oil of my invention the proportions may, for example, varybetween about 5% and 1 75% by volume of naphthenic acid to between about95% and of mineral lubricating oil. For most purposes compositionscontaining from about 10% to about 50% by volume of naphthenic acid giveexcellent results.

The mineral lubricating oil and naphthenic acid are mixed together toform a solution and the metallic naphthenate may, if desired, beseparately prepared and added to the resulting solution. According to apreferred procedure, however, I may form the metallic naphthenate in thelubricating oil-naphthenic acid solution by contact thereof with acompound of the desired metal which will react with a portion of thenaphthenic acid to form metallic naphthenate.

Various metallic naphthenates may be employed such as those ofmagnesium, calcium, aluminum, lead, manganese, copper, iron, cobalt ornickel. Mixtures of two or more of these metallic naphthenates may alsobe used.

The proportion of metallic naphthenate in the cutting oil compositionshould be at least /2% by weight, and I prefer to use from about 1% toabout 5% metallic naphthenate.

Naphthenates of theabove mentioned metals may be prepared by heating theoxide of such metal with naphthenic acid, or by reacting sodiumnaphthenate with a solution of a soluble salt of the metal. For example,in preparing magnesium naphthenate I may heat magnesium oxide withnaphthenic acid, or I may first react sodium hydroxide with naphthenicacid to form sodium naphthenate and then subject the latter to contactwith a solution of magnesium sulphate or magnesium chloride to formmagnesium naphthenate.

In the making of my cutting oil composition, the lubricating oil andnaphthenic acid may be either crudeor refined. Since there isconsiderable difference in price between the crude and mixture.

refined products, I generally prefer to use the cheaper, unrefinedmaterials and to refine them by treatment with sulphuric acid to removeasphaltic or gum-forming impurities. In the refining process, thematerials may be treated separately and subsequently mixed, or themixture may be made prior to the refining process, a procedure which Iprefer. As an example of this procedure, I first mix thoroughly in thedesired proportions, a crude lubricating stock and a crude naphthenicacid of the desired acid number. This mixture is then treated with fromone to ten pounds of 66 B. sulphuric acid per barrel (of 42 U. S.gallons) of the mixture, and the whole thoroughly agitated for ten tofifteen minutes, which is sufficient to remove the impurities but notsuflicient to cause sulfonation of the naphthenic acids, since it iswell known that these sulfonation reactions proceed quite slowly. Afterthe agitation, the acid sludge is allowed to settle and is drawn oilfrom the bottom of the container or the oil mixture may be decanted fromthe sludge.

The resulting refined mixture may then be subjected to filtration in anydesired manner to remove any suspended acid sludge or any otherundissolved impurities, and is preferably then treated with caustic sodasolution to neutralize any free sulphuric acid or sulphur dioxide, afterwhich the desired proportion of metallic naphthenate produced asdescribed above may be aned and the whole mixture thoroughly agitated touniformly distribute the metallic naphthenate, either in solution or inthe form of a colloidal dispersion. As an alternative, the metallicnaphthenate may be incorporated in the mixture prior to the filtrationstep.

An example of a cutting oil prepared by mixing and treating theingredients as described above is one containing 25 parts by volume ofnaphthenic acid to '15 parts of mineral lubricating oil together with 2to 2 /2% by weight of metallic naphthenate based on the total weight ofthe mixture. The metallic naphthenate may, for example, be magnesiumnaphthenate, calcium naphthenate, or aluminum naphthenate.

According to the preferred procedure mentioned above, metallicnaphthenate may be formed in the refined lubricating oil-naphthenic acidmixture by contact of such mixture with an oxide, silicate, or otherreactive compound of the desired metal. In following this procedure, Ifind it especially advantageous to employ a compound of the desiredmetal which is also capable of acting as a filter aid and also as anadsorbent material for decolorizing the mixture.

As a specific example of this preferred method of preparation, a mixtureis made containing 20% by volume of naphthenic acid and 80% by volume ofmineral lubricating oil. Th s mixture is treated with 66 B.sulphuricacid and thoroughly agitated to remove asphaltic and gumformingconstituents, after which the sludge is allowed to settle and is drawnoff. The refined mixture is then heated to approximately 130 F.. and ahydrated magnesium silicate is added in the proportion of about 3% byweight of the The mixture is then agitated well for a sufficient periodto cause partial reaction between the magnesium silicate and thenaphthenic acid to form the desired proportion of magnesium naphthenate,for example, for about two to four hours. The mixture is then filteredto remove the unreacted magnesium silicate and other undissolved solids.

The magnesium silicate is preferably one which has a high adsorbentpower, such as a synthetic hydrated magnesium silicate sold under thetrade name of Magnesol, which acts not only to produce magnesiumnaphthenate in the solution by partial reaction with the naphthenic acidbut also as a filter aid and adsorbent to remove both suspended solidsand color from the mixture.

A cutting oil composition prepared by the specific procedure describedabove, using Magnesol, was found to contain about 1/2% of magnesiumnaphthenate together with somewhat less than 1% of iron naphthenate, thelatter probably resulting from reaction of the naphthenic acid with theiron vessels and equipment employed in the process.

It will be understood of course that other materials in addition tothose mentioned above may also be added to the composition if desired.without departing from the scope of my invention. However, I have foundthat compositions containing only the above mentioned ingredients withinthe specified ranges give very excellent results when used as cuttingoils. The manner of applying and using such compositions may beessentially the same heretofore employed with other cutting oilcompositions.

I claim:

. l. A cutting oil consisting principally of mineral lubricating oil andnaphthenic acid in proportions between 5% and naphthenic acid to between95% and 25% mineral lubricating oil. by volume, and also containing from/z% to about 5 by weight of metallic naphthenate.

2. A cutting oil consisting principally of mineral lubricating oil andnaphthenic acid in proportions between 5% and 75% naphthenic acid tobetween 95% and 25% minerallubricating oil. by volume, and alsocontaining from 1% to 5% by weight of metallic naphthenate.

3. A cutting oil consisting principally of mineral lubricating oil andnaphthenic acid in proportions between 10% and 50% naphthenic acid tobetween and 50% mineral lubricating oil, by volume, and also containingfrom /2% to about 5% by weight of metallic naphthenate, said naphthenicacid having an acid number between about 75 and 3'75.

4. A cutting oil consisting principally of m neral lubricating oil andnaphthenic acid in proportions between 10% and 50% naphthenic acid tobetween 90% and 50% mineral lubricating oil, by volume, and alsocontaining from 1% to5% by weight of metallic naphthenate.

5. A cutting oil consisting principally of mineral lubricating oil andnaphthenic acid in pro-

